Microsoft Corp. risks European Union penalties for failing to comply with a settlement to give users a choice of web browsers, more than two years after it tried to end a decade-long clash with antitrust regulators.

EU Competition Commission Joaquin Almunia said Microsoft may have misled regulators by failing to display a browser choice screen to users of the Windows operating system since February 2011. The world's largest software company blamed a technical error for not showing the screen to some users and offered to extend its commitment until March 2016.

Microsoft has already been fined 1.68 billion euros ($2.06 billion) in EU antitrust probes. The Redmond, Washington-based company agreed to offer access to rival browsers as a part of a settlement to repair its relationship with the bloc's regulators. Microsoft has more recently filed complaints against Google Inc. and what is now its Motorola Mobility unit for alleged antitrust violations.

"I trusted that the company's reports were accurate," EU Competition Commissioner Joaquin Almunia said in an e-mailed statement. "If following our investigation, the infringement was confirmed, Microsoft should expect sanctions."

Deep "˜regret'

Microsoft told regulators in December 2011 that it was obeying its commitments even though it may have dropped the browser screen in Windows 7's Service Pack 1 earlier in the year, the EU said. The company can be fined as much as 10 percent of yearly revenue for breaching the terms of its settlement.

"We learned recently that we've missed serving the browser choice screen software to the roughly 28 million personal computers running Windows 7 Service Pack 1," Microsoft said in an e-mailed statement. "We deeply regret that this error occurred and we apologize for it."

Under the terms of Microsoft's 2009 pledge, consumers who buy personal computers were given a choice of the 12 most widely used browsers to install in addition to, or instead of, Microsoft's Internet Explorer.

Google's Chrome was the most popular web browser globally in June, with 32.8 percent of market share, according to statistics from web analytics firm StatCounter. Microsoft's Internet Explorer followed with 32.3 percent. Mozilla Corp.'s Firefox accounted for about a quarter of users.

Microsoft's shares increased 1.1 percent to $29.76 at 9:38 a.m. in New York. Through yesterday, the stock had advanced 13 percent this year.